NASA Comet-Chasing Probe Closes in on Icy Valentine

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After more than three years of preparation, waiting and chasing,
a NASA probe is now just days away from its Valentine's Day date
with a comet.

The Stardust-NExT spacecraft will fly to within 124 miles (200
kilometers) of comet Tempel 1 at about 11:40 p.m. EST on the
night of Feb. 14 (0440 GMT on Feb. 15). The main goal is to see
how much Tempel 1 has changed since July 2005, when NASA's Deep
Impact probe flew by the icy wanderer and sent an impactor
smashing into it.

"The primary purpose is to observe how the comet has changed, how
the nucleus has changed, to compare to what it was like back in
2005," said Stardust-NExT project manager Tim Larson, of NASA's
Jet Propulsion Laboratory in Pasadena, Calif., in a recent NASA
video.

Repurposed spacecraft

The Stardust-NExT probe began its life as the Stardust
spacecraft, which launched in February 1999. It accomplished its
primary mission — to collect dust and gas from around comet Wild
2 and send the sample back to Earth in a return canister — in
2006.

Since the spacecraft was in good shape and had enough fuel, NASA
gave it a new mission in July 2007: to meet up with comet Tempel
1. With the new mission came an expanded name: Stardust-NExT (for
"New Exploration of Tempel").

The 3.7-mile-wide (6 km) comet completes an orbit every 5 1/2
years, so it has circled the sun once since Deep Impact's visit.
Researchers hope Stardust-NExT will give them an idea of how
Tempel 1 has changed during this time.

Another goal is to map out more of Tempel 1's surface, adding to
the work done by Deep Impact. Through making these and other
observations, Stardust-NExT can contribute to scientists'
understanding of how comets formed at the solar system's birth
4.6 billion years ago and how they have evolved since then,
researchers have said.

Well-traveled probe

Stardust-NExT has already logged about 3.5 billion miles (5.7
billion km) in space, researchers said, and it will put a few
more on its odometer before calling it quits.

On the night of Feb. 14, the spacecraft — traveling at about
24,300 mph (39,100 kph) — will fly close to within 124 miles (200
km) of Tempel 1. Stardust-NExT will take 72 high-resolution
images during the flyby and begin transmitting them to Earth
about an hour after the closest approach, researchers said.

This should be the last comet encounter for Stardust-NExT. It
will burn up almost all of its remaining fuel chasing down Tempel
1. But it should go out on a high note, researchers said.

"The spacecraft is working wonderfully well," Stardust-NExT
principal investigator Joe Veverka, of Cornell University, told
reporters last month. "The science team is awfully excited and
can't wait to see all the pictures."